The objective of the work was to compare the socioeconomic situation and the structure of tobacco use in the families of children attending preschools in Bialystok in 2004 and 2012 in terms of 3-year-olds' exposure to environmental tobacco smoke (ETS). The study involved 313 children out of 1,200 3-year-olds attending 51 pre-schools in Bialystok in 2004 (Gr I) and 273 children out of 1,100 attending 49 pre-schools in 2012 (Gr I). Information on environmental conditions and the use of tobacco in the families of the studied 3-year-olds was obtained through anonymous questionnaires filled in by their parents or caregivers. The exposure of children to ETS was evaluated using the questionnaire and by determining the cotinine/creatinine ratio in urine. The children from Gr I had better educated (p<0.001) and wealthier (p=0.005) parents, and better living conditions (p=0.008). In 47.3% of the homes of children from Gr I and 31.1% of homes of children from Gr II there was at least one smoking person (p<0.001). Both in 2004 and in 2012, fathers prevailed among the smokers, but in 2012 their number was significantly lower (p<0.001). As for mothers, 23.6% of them in Gr I and 10.3% in Gr I admitted smoking every day (p<0.001). More children from Gr I than from Gr I lived with smoking grandparents. The declared number of cigarettes smoked a day by the people living with the children was similar in both Groups The Groups did not differ significantly regarding the rules of tobacco smoke applying to the family members and guests (p=0.639). The mean cotinine/ creatinine concentration [ng/mg] in the urine of children from Gr I (60.78) was significantly higher than in those from Gr II (22.75) (p<0.001). According to the survey data, in 2012 fewer three-year-olds were exposed to ETS out of home (p<0.001). The mean cotinine/ creatinine concentrations [ng/mg] depending on the declared exposure to tobacco smoke out of home: no exposure, existing exposure, unknown exposure, were for Gr I and Gr II, respectively: 51.31 vs. 35.67; (p<0.001), 76.10 vs. 38.65; (p=0.002), 76.92 vs. 47.04; (p=0.460). In 2012, as compared to 2004, the number of smokers among young parents decreased, but despite education activities in the community, only 1/4 of homes with children had the "no smoking" rule.